1. Field of the Invention
The present invention relates to an improved crucible used in an analyzer for quantitatively analyzing elements contained in a sample such as metallic materials and ceramics.
2. Description of Related Art
In an analyzer for quantitatively analyzing elements contained in a sample such as metallic materials and ceramics, usually a graphite crucible is positioned between a set of electrodes which are arranged in a vertical manner within a sample-extracting furnace under airtight conditions. The sample is put in the graphite crucible, and a large electric current is passed between both electrodes while supplying an inert gas as a carrier gas to heat the graphite crucible. The sample is melted and generates a sample gas which is collected in an analyzer to enable an analysis of the elements in the sample.
Prior to such an analysis of the elements, the graphite crucible is heated to high temperatures prior to introducing the sample to conduct a degassing treatment, also called preheating, for removing impurities such as various gases including water.
However, in the above-described degassing treatment, while the graphite crucible is heated to high temperatures of about 3,000.degree. C., an upper electrode made of copper alloys is strongly cooled with water, so that a temperature in the vicinity of the upper electrode is not as high. Thus, a sufficient degassing cannot be achieved. As a result, gaseous elements to be measured, such as CO, N, and H, may remain in an upper portion of the graphite crucible.
In such a case, when the sample is put in the graphite crucible to extract the sample gas, the molten sample rises to an upper portion of the graphite crucible to release any gaseous elements remaining in the graphite crucible. Therefore, a problem has occurred in that the gaseous elements are collected in the analyzer together with sample elements released from the sample itself. Thus, accurate analytical values are not obtained and reliability is lowered.
In order to solve such a problem, a so-called double crucible capable of indirectly heating the sample has been used. Such a system is disposable; therefore, another problem has occurred in that cost is increased.